The present invention relates to a limited-area reflection type optical sensor in which a sensing area of an object is limited and an electronic device.
Conventionally, a limited-area reflection type optical sensor in which a sensing area of an object is limited is known as an optical sensor that detects whether the object exists at a predetermined position.
As illustrated in FIGS. 16A and 16B, a limited-area reflection type optical sensor 100 includes a light emitting element 101 and a light receiving element 102. In the light emitting element 101 and the light receiving element 102, an angle between the optical axes are set such that the object sensing limited area S is irradiated with the light emitted from the light emitting element 101, and such that the light receiving element 102 can receive the light reflected from the object, the light reflected from the object intersecting the emitted light only in the object sensing limited area S. When the object passes through the object sensing limited area S indicated by a hatch, the light reflected from the object is detected by the light receiving element 102 to determine the object.
Particularly, in the limited-area reflection type optical sensor 100, in the case that the object exists in the object sensing limited area S of distances LL2 to LL4 from the limited-area reflection type optical sensor 100, the emitted light from the light emitting element 101 is specularly reflected by the object, and the specularly-reflected light is incident to the light receiving element 102. However, a determination that the object does not exist is made in the case that the object exists out of the object sensing limited area S of the distances LL2 to LL4. Accordingly, a range of the distances LL2 to LL4 becomes an object detection range. Thus, in the limited-area reflection type optical sensor 100, the light receiving element 102 obtains a signal in the case that the object reaches the object sensing limited area S of the distances LL2 to LL4, whether the object exists is determined based on the signal.
At this point, in the limited-area reflection type optical sensor 100, in the case that the emitted light and the reflected light do not have spread, a distance between an operation level at which the object is detected to output a detection signal and a non-operation level at which the object moves to become a non-detection state is small and an influence of a background decreases. One of features of the limited-area reflection type optical sensor 100 is that a detection distance can be set by changing an angle between optical axes of the light emitting element 101 and the light receiving element 102.
However, for example, the conventional limited-area reflection type optical sensor 100 is used to detect the approaching object to stop the object at a given position. Therefore, as illustrated in FIGS. 16A and 16B, the emitted light and the reflected light is formed at the distance LL4 which is the position separated from the limited-area reflection type optical sensor 100.
However, in the conventional limited-area reflection type optical sensor, there is a problem in that the detection range is not wide.
For example, Japanese Unexamined Patent Publication No. 6-241783 discloses an optical sensor 200 that can widen the detection range. In the optical sensor 200, as illustrated in FIG. 17, plural reflection type optical sensors 201A to 201D are provided in parallel in order to detect surfaces to be measured A to D at a detection position P, and the surfaces to be measured A to D are separately detected by the reflection type optical sensors 201A to 201D. In order to detect the surfaces to be measured A to D, the optical sensor 200 includes the reflection type optical sensors 201A to 201D, projectors 202, and optical receivers 203, respectively. As a result, the detection range can be widened.
However, in the optical sensor 200 disclosed in Japanese Unexamined Patent Publication No. 6-241783, unfortunately the device is enlarged because the sensors are provided according to the number of surfaces to be measured. When the sensors are installed near each other, unfortunately the adjacent sensors interfere with each other to generate a malfunction.
An object of the invention is to provide a simple-configuration limited-area reflection type optical sensor that can accurately detect the object, in which the distance to the surface to be measured changes, by widening the detection range in a far-and-near direction and an electronic device.